Severe Thunderstorm Warning 22, NWS Grand Junction, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
332 PM MDT WED SEP 18 2013

.SHORT TERM...(TONIGHT THROUGH THURSDAY NIGHT)
ISSUED AT 332 PM MDT WED SEP 18 2013

TROUGH MOVING ACROSS THE NORTHERN MOUNTAIN STATES DROVE A COLD
FRONT INTO NORTHWEST COLORADO THIS AFTERNOON. RELATIVELY WEAK
SOUTHWEST TO NORTHEAST ORIENTED JET PROVIDED SHEAR FOR LONG TRACK
THUNDERSTORMS WITH ONE STORM SOUTH OF BLANDING GENERATING NEAR
SEVERE HAIL. SPOTTERS A BIT NORTH OF THE HAIL CORE...SO POSSIBLE
WARNING FOR THIS STORM WILL VERIFY YET.

WBZ...SHEAR AND UPPER LEVEL SUPPORT SHOULD CONTINUE TO SUPPORT
ORGANIZED CONVECTION WELL INTO THE EVENING AS THE TROUGH CONTINUES
TO SWEEP EASTWARD. THEREFORE...BOOSTED POPS LATER INTO THE EVENING
BEFORE TAPERING LATER TONIGHT. TROUGH PASSAGE WILL FORCE THE COLD
FRONT SOUTH OF THE I-70 CORRIDOR LATE TONIGHT WITH CLEARING ON THE
BACKSIDE. TEMPERATURES WILL BE COOLER OVERNIGHT NORTH AND NEAR
PERSISTENCE SOUTH OF THE FRONT.

TROUGH AXIS PASSES EAST OF THE DIVIDE THURSDAY AFTERNOON WITH MUCH
DRIER AIR FOLLOWING IN ITS WAKE. PROBABLY ENOUGH MOISTURE LINGERING
FOR ISOLATED CONVECTION ALONG THE DIVIDE MOUNTAINS DURING THE
AFTERNOON...OTHERWISE EXPECTING QUIET WEATHER ACROSS THE FORECAST
AREA WITH HIGHS RUNNING 4 TO 8 DEGREES COOLER. COLDER AIR CONTINUES
TO FILTER INTO THE REGION THURSDAY NIGHT WHICH...WITH CLEARING
SKIES...THREATENS TO BRING FREEZING TEMPERATURES TO THE LOWER
VALLEYS ALONG THE YAMPA RIVER INCLUDING CRAIG. MODELS SUGGEST
FREEZE WILL BE FAIRLY LOCALIZED...BUT WILL GO AHEAD WITH A FREEZE
WATCH TO RAISE PUBLIC AWARENESS.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 332 PM MDT WED SEP 18 2013

PROGRESSIVE PATTERN CONTINUES THROUGH THESE PERIODS BEGINNING WITH
A RIDGE ON FRIDAY THEN A TROUGH PASSAGE SUNDAY AND A MUCH DEEPER
AND COLDER TROUGH CURRENTLY FORECAST FOR NEXT THURSDAY.

AFTER AN UNSEASONABLY COOL MORNING FRIDAY...AFTERNOON TEMPERATURES
WILL RISE TO ABOVE NORMAL. FLOW ALOFT WILL BACK FROM NW TO SW THAT
WILL PULL MOISTURE BACK INTO THE SOUTHERN ZONES FRIDAY NIGHT INTO
SATURDAY. PRECIPITABLE WATER VALUES RISE TO GREATER THAN 0.75 INCH
IN THE FOUR CORNERS AND FURTHER TO THE NORTH IN THE WETTER NAM.

STORM MOTION ON SATURDAY INTO SUNDAY WILL AGAIN BE BRISK... TO THE
NE AT 35 MPH. WET BULB ZERO LEVEL WILL BE AT OR BELOW 13KFT... LOW
ENOUGH TO SUPPORT HAIL. SO THERE IS SOME RISK OF SEVERE
THUNDERSTORMS FAVORING THE SOUTHERN AND CENTRAL FORECAST ZONES.
THE UPPER TROUGH AND COOL FRONT PASS SUNDAY NIGHT...FOR MORE
STABLE CONDITIONS.

MONDAY-TUESDAY...A FLAT ZONAL FLOW REMAINS OVER THE INTERMOUNTAIN
WEST AS THE NEXT DEEPER TROUGH DEVELOPS IN THE EASTERN PACIFIC
THEN MAKES LANDFALL IN THE PACIFIC NW. MARGINAL MOISTURE REMAINS IN
PLACE FOR MAINLY LATE-DAY SHOWERS AND STORMS.

WEDNESDAY THE TROUGH DIGS INTO THE GREAT BASIN. WEST FLOW BACKS TO
SW AND INCREASES TO 50KTS AT 500MB. PRECIPITABLE WATER VALUES
REMAIN AT AROUND 0.5 INCH BUT ANY VIRGA SHOWERS COULD PRODUCE VERY
STRONG SURFACE WINDS. THIS TROUGH WILL HAVE A SIGNIFICANT COLD
CORE...THE FIRST OF THE SEASON. THE EC AND GFS ARE IN GOOD
AGREEMENT WITH TEMPS AT 500/700 AT -20/-4C. THIS MODIFIES AND
WEAKENS SOME AS IT MOVES OVER THE REGION NEXT THURSDAY...BUT
SNOWFALL ABOVE 8000FT LOOKS POSSIBLE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 332 PM MDT WED SEP 18 2013

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THE
EVENING SOUTHEAST OF A KCNY TO KCAG LINE. HIGHER TERRAIN WILL BE
FAVORED BUT SEVERAL STORM CELLS WILL MOVE OUT OVER ADJACENT
VALLEYS. STORM ACTIVITY WILL RESULT IN AREAS OF MOUNTAIN
OBSCURATION AND WIND GUSTS FROM 35 TO 45 MPH WITH A 3O TO 50
PERCENT CHANCE FOR MVFR VSBY IN HEAVY RAIN AT AIRPORTS EAST OF A
KCEZ-KCAG LINE. STORM ACTIVITY WILL DECREASE AFTER 06Z WITH VFR
CONDITIONS RETURNING REGION WIDE BY BY 08Z. A FEW SHOWERS MAY
LINGER OVER THE SAN JUANS THROUGH 12Z THOUGH IT IS UNLIKELY THAT
THIS WILL IMPACT FLIGHT CONDITIONS. EXCEPT FOR A FEW STORMS
FORMING OVER THE CONTINENTAL DIVIDE AFTER 18Z...VFR CONDITIONS
WILL BE THE RULE THURSDAY AFTERNOON.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...FREEZE WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY MORNING FOR
     COZ002.

UT...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR UTZ027.

&&

SHORT TERM...NL
LONG TERM...JOE
AVIATION...NL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
558 AM MDT WED SEP 18 2013

COZ001>014-017>023-UTZ022>025-027>029-191200-
LOWER YAMPA RIVER BASIN-CENTRAL YAMPA RIVER BASIN-
ROAN AND TAVAPUTS PLATEAUS-ELKHEAD AND PARK MOUNTAINS-
UPPER YAMPA RIVER BASIN-GRAND VALLEY-DEBEQUE TO SILT CORRIDOR-
CENTRAL COLORADO RIVER BASIN-GRAND AND BATTLEMENT MESAS-
GORE AND ELK MOUNTAINS/CENTRAL MOUNTAIN VALLEYS-
CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN-
WEST ELK AND SAWATCH MOUNTAINS-FLATTOPS-
UPPER GUNNISON RIVER VALLEY-UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-
NORTHWEST SAN JUAN MOUNTAINS-SOUTHWEST SAN JUAN MOUNTAINS-
PARADOX VALLEY/LOWER DOLORES RIVER-
FOUR CORNERS/UPPER DOLORES RIVER-ANIMAS RIVER BASIN-
SAN JUAN RIVER BASIN-SOUTHEAST UTAH-EASTERN UINTA MOUNTAINS-
EASTERN UINTA BASIN-TAVAPUTS PLATEAU-ARCHES/GRAND FLAT-
LA SAL AND ABAJO MOUNTAINS-CANYONLANDS/NATURAL BRIDGES-
558 AM MDT WED SEP 18 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN UTAH AND WESTERN
COLORADO.

.DAY ONE...TODAY AND TONIGHT

A COLD FRONT WILL MOVE OVER THE AREA TODAY AND AHEAD OF THE FRONT
SOME SHOWERS AND STORMS ARE POSSIBLE. SOME HAIL AND GUSTY WINDS
WILL BE POSSIBLE UNDER THE STRONGER STORMS. SOME GUSTY AFTERNOON
WINDS WILL ALSO BE POSSIBLE AHEAD OF THE COLD FRONT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

MOSTLY CLEAR SKIES EXPECTED THROUGH TUESDAY WITH A CHANCE FOR SOME
SHOWERS SUNDAY AFTERNOON AND EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
343 PM MDT WED SEP 18 2013

COZ009-011-012-182230-
CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN CO-GRAND AND BATTLEMENT
MESAS CO-WEST ELK AND SAWATCH MOUNTAINS CO-
343 PM MDT WED SEP 18 2013

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN DELTA...WESTERN
GUNNISON AND EXTREME NORTHERN MONTROSE COUNTIES UNTIL 430 PM MDT...

AT 343 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 8 MILES SOUTHEAST OF ORCHARD CITY...OR 17 MILES
NORTH OF MONTROSE...MOVING EAST AT 40 MPH.

HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  HOTCHKISS...
  CRAWFORD...
  PAONIA...
  LAZEAR...
  BOWIE...
  SOMERSET...

TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND
UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED
ROADWAY.

LAT...LON 3866 10771 3867 10785 3863 10784 3860 10795
      3877 10803 3901 10739 3878 10728

TR

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
346 PM MDT WED SEP 18 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0740 PM     HAIL             3 NW BROWNS PARK        40.81N 108.89W
09/17/2013  E0.75 INCH       MOFFAT             CO   OTHER FEDERAL

            ADAM HABORSON AT BROWNS PARK NATIONAL WILDLIFE REFUGE
            REPORTED 3 4 INCH HAIL THAT DAMAGED VEHICLES AND
            FLOODING OF BASEMENTS. THE FLOODING IS PRIMARILY DUE TO
            SATURATED SOILS.

0740 PM     FLASH FLOOD      3 NW BROWNS PARK        40.81N 108.89W
09/17/2013                   MOFFAT             CO   OTHER FEDERAL

            ADAM HABORSON AT BROWNS PARK NATIONAL WILDLIFE REFUGE
            REPORTED 3 4 INCH HAIL THAT DAMAGED VEHICLES AND
            FLOODING OF BASEMENTS. THE FLOODING IS PRIMARILY DUE TO
            SATURATED SOILS.

&&

EVENT NUMBER GJT1301543
EVENT NUMBER GJT1301544

JOE

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